scholarly journals Reduction of the Local Stress Field around Holes through Porous Shaped Structures

2018 ◽  
Vol 20 (3) ◽  
pp. 36-41
Author(s):  
Stefano Monti
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Stress Field ◽  
Present Article ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Laser Cutting ◽  
Local Stress ◽  
Hole Boundary ◽  
Local Stress Field

Geometrical discontinuities in mechanical components are detrimental for the mechanical properties of the product itself. Actually, in proximity of such features, the stress increases due to the stress concentration factor, that in the case of a circular hole is equal to 3. Several solutions have been proposed to reduce the stress concentration value. In the present article, the application of a particular porous pattern that can be obtained by laser cutting with the appropriate finishing requirements is introduced in order to modify the local stress field and reduce the stress concentration value near the hole boundary.

Effects of Microstructure on Cavity Nucleation in Creeping Ceramics Containing Viscous Grain Boundary Phase

2008 ◽  
Vol 368-372 ◽  
pp. 1084-1087
Author(s):  
Chao Wang ◽  
Jun Liang ◽  
Yang Liu ◽  
Jie Cai Han
Keyword(s):  
Stress Concentration ◽  
Grain Boundary ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Critical Stress ◽  
Local Stress ◽  
Viscosity Coefficient ◽  
Boundary Phase ◽  
Cavity Nucleation ◽  
Grain Sizes

A theoretical model considering the distribution of the grain sizes and grain-boundary ledges was developed for cavity nucleation in creeping ceramics containing viscous grain boundary phase. The critical stress involving the effects of various shapes of cavities and viscosity coefficient (η) for cavity nucleation was presented. Then, the local stress concentration factor concerning different distributions of grain-boundary ledges was calculated and discussed. The results showed that various shapes of cavities and η are not the main influencing factors on the critical stress. The stress concentration factor increases with the increase of grain-boundary ledge size or the density. Therefore, it would be liable to cause cavity nucleation at gain boundary when the density of grain-boundary ledges is high and the size is large.

Influence of the Notch Rounding Radius on Estimating the Elastic Notch Stress Concentration Factor in a Laser Welded Tee Joint

2012 ◽  
Vol 726 ◽  
pp. 100-105 ◽  
Author(s):  
Karol Niklas ◽  
Janusz Kozak
Keyword(s):  
Stress Concentration ◽  
Laser Welding ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Local Stress ◽  
Thin Plates ◽  
Outer Side ◽  
Notch Stress ◽  
Sandwich Type ◽  
Welding Technique

In recent years an increased interest of industry in sandwich-type metal structures can be observed. These structures consist of thin plates of 2.5 mm in thickness separated by stiffeners of different shapes and forms. Welds joining the plates and stiffeners are made on the outer side of the plates using laser welding technique. A locally focused source of heat causes the plate to melt creating a very narrow and elongated joint. As a result, sharp geometric notches are formed on the side of the root of a weld – a place which is inaccessible and cannot be checked. Geometries of individual welded joints vary, sometimes considerably, and this makes their analysis even more complicated. Additionally, the use of laser welding technique influences the formation of untypical distribution of changes in material properties in weld zones. The effect is a joint whose behaviour under load is significantly different from the behaviour of a welded tee joint made with the use of classical methods. Fatigue strength calculations for this type of joints can be conducted based on local stress values in notches, which can be determined with the use of Finite Element Method (FEM). This article analyses the influence of the notch rounding radius on the elastic notch stress concentration factor Kt The aim of the analysis is to evaluate the notch stress concentration according to local notch stress approach.

Stress Concentration at a Nearly Circular Hole With Uncertain Irregularities

1992 ◽  
Vol 59 (2S) ◽  
pp. S65-S71 ◽  
Author(s):  
Dan Givoli ◽  
Isaac Elishakoff
Keyword(s):  
Stress Concentration ◽  
Circular Hole ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Maximum Stress ◽  
Polar Coordinates ◽  
Elastic Plane ◽  
Worst Case ◽  
Hole Profile ◽  
Hole Boundary

We study the stress concentration on the boundary of an uncertain nearly circular hole in an infinite elastic plane under uniform radial tension at infinity. The uncertainty in the deviation of the hole profile from an ideal circle is modeled deterministically. The shape of the hole boundary in polar coordinates is assumed to have the form r = R + εh(θ), where R is the radius of the unperturbed circle and ε is a small parameter. First, we find an asymptotic solution for the stress concentration factor around the hole for any profile h(θ). Then we consider a certain set of bounded profiles, and we find the specific profile that yields the maximum stress concentration factor. This may provide the designer with a useful “worst case” information regarding the influence of the uncertainty of the hole shape on the uncertainty of the resulting stress concentration factor.

Analysis of strain and stress concentrations in micro-lattice structures manufactured by SLM

2019 ◽  
Vol 26 (2) ◽  
pp. 370-380 ◽  
Author(s):  
Laura Boniotti ◽  
Stefano Foletti ◽  
Stefano Beretta ◽  
Luca Patriarca
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Content Type ◽  
Lattice Materials ◽  
Geometrical Imperfections

Purpose Additive manufacturing (AM) enables the production of lightweight parts with complex shapes and small dimensions. Recent improvements in AM techniques have allowed a significant growth of AM for industrial applications. In particular, AM is suitable for the production of materials shaped in lattice, which are very attractive for their lightweight design and their multi-functional properties. AM parts are often characterised by geometrical imperfections, residual porosity, high surface roughness which typically lead to stress/strain localisations and decreasing the resistance of the structure. This paper aims to focus on the study of the effects of geometrical irregularities and stress concentrations derived from them. Design/methodology/approach In this paper, several technique were combined: 3D tomography, experimental tests, digital image correlation and finite elements (FE) models based on both the as-designed and the as-manufactured geometries of lattice materials. The Digital Image Correlation technique allowed to measure local deformations in the specimen during the experimental test. The micro-computed tomography allowed to reconstruct the as-manufactured geometries of the specimens, from which the geometrical quality of the micro-structure is evaluated to run FE analyses. Findings Experimental and numerical results were compared by means of a stress concentration factor. This factor was calculated in three different specimens obtained from three-different printing processes to compare and understand their mechanical properties. Considering the as-designed geometry, it is not possible to model geometrical imperfections, and a FE model based on an as-manufactured geometry is needed. The results show that the mechanical properties of the printed samples are directly related to the statistical distribution of the stress concentration factor. Originality/value In this work, several techniques were combined to study the mechanical behaviour of lattice micro-structures. Lattice materials obtained by different selective laser melting printing parameters show different mechanical behaviours. A stress concentration factor can be assumed as a measure of the quality of these mechanical properties.

Photoelastic Investigation on Plates with Single Interference-Fit Pins with Load Applied to Plate Only

1956 ◽  
Vol 7 (4) ◽  
pp. 297-314 ◽  
Author(s):  
H. T. Jessop ◽  
C. Snell ◽  
G. S. Holister
Keyword(s):  
Stress Concentration ◽  
Flat Plate ◽  
Circular Hole ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Hole Diameter ◽  
Interference Fit ◽  
Applied Tension ◽  
Photoelastic Investigation ◽  
Hole Boundary

SummaryThe introduction of an interference-fit pin in a circular hole in a flat plate is found to result in a reduction in the stress concentration factor at the hole boundary under tension applied to the plate. The S.C.F. decreases rapidly with increase in the ratio of interference stress to applied tension, and decreases also with increase in the ratio of hole diameter to width of plate. Very little difference in the S.C.F. is found for different ratios of Young's modulus of pin and plate.

scholarly journals A novel thread connection structure of slimehole drilling tool in ultra-deep natural gas well

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110264
Author(s):  
Zhang Ying ◽  
Lian Zhanghua ◽  
Gao Anqi ◽  
Yang Kun
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Sensitivity Coefficient ◽  
Notch Sensitivity ◽  
Sensitivity Factor ◽  
Drilling Tool ◽  
Gas Well ◽  
Thread Connection

The thread connection’s root fillet radius of 0.038″ size is the greatest weakness of the API NC type joints and thread. During the slimehole drilling, especially in the deep and ultra-deep gas well, its stress concentration factor and notch sensitivity factor are very high A novel thread connection design (TM) of a drilling tool is proposed to decrease the fatigue failure of the slimehole drilling tool in the deep and the ultra-deep gas well in the Tarim oilfield China. The novelty in the TM thread structure is, reducing the threads per inch, extending the distance from the last engaged thread to the external shoulder of the pin and adding three threads to the conventional connection. The novel thread connection will improve the slimehole drilling tool’s anti-fatigue life due to its improved elasticity and rigidity. Furthermore, the TM can transfer the maximum stress at the connection root to the loaded surface, which can effectively lower the fatigue notch’s sensitivity coefficient. In this paper, the finite element method (FEM) is applied to carry out the detailed comparative analysis of the TM with existing thread connection NC38, TX60 and TH90. The TM has the lowest stress concentration factor and fatigue notch sensitivity coefficient, so its anti-fatigue life is the highest. In addition, TM is manufactured and is tested at Tarim oilfield in China.

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